Method and apparatus for establishing the firing temperature curve of a sintering charge

ABSTRACT

The firing temperature curve of a sintering charge is established by measuring the speed of the chain which carries successive portions of the charge and the temperature of the gases which have passed through the fired portions of the charge at points spaced longitudinally in the direction of the movement of the chain. The measurements are coordinated so that the temperature measurement depends on the speed movement, and the temperature measurements are periodically sampled after a series of such measurements has been completed. The corresponding information is stored in a memory and extracted from the memory after the completion of each series to obtain the firing temperature curve.

United States Patent [1 1 [111 3,779,077 Barry et al. Dec. 18, 1973 METHOD AND APPARATUS FOR lection Chart; December 12, 1962.

ESTABLISHING THE FIRING TEMPERATURE CURVE OF A SINTERING CHARGE Primary Examiner-Richard C. Queisser Assistant Examiner-Denis E. Corr [75] Inventors: Claude Barry, Samt-Jullen-les-Metz; AttorneynKurt Kelman Patrice Ratte, Metz, both of France [73] Assignee: Institut De Recherches De La Siderurgie Francaise, Saint Germain-en-Laye, France [57] TR [22] Filed: 1972 The firing temperature curve of a sintering charge is [21] Appl. No.: 242,361 established by measuring the speed of the chain which carries successive portions of the charge and the temperature of the gases which have passed through the 2% 8 25 31 2 fired portions of the charge at points spaced longitudi- {58% Se-1d o'f 340 343 nally in the direction of the movement of the chain.

263/28 The measurements are coordinated so that the temperature measurement depends on the speed movement, and the temperature measurements are periodi- [56] References cued cally sampled after a series of such measurements has UNITED STATES PATENTS been completed. The corresponding information is 2,878,003 3/1959 Dykeman 73/34l stored in a memory and extracted from the memory 3,622,140 1 H1971 Schwestka 73/34! after the completion of each series to obtain the firing 3,194,546 7/1965 Schuerger 263/28 temperature curve OTHER- PUBLICATIONS Trinity Temperature Products Catalog; Materials Se- 4 Claims, 3 Drawing Figures 2 I 4 twin-s a tintene ,1 I H {A PATENTEI] DEE I 8 I975 sum 2 OF 2 METHOD AND APPARATUS FOR ESTABLISHING THE FIRING TEMPERATURE CURVE OF A SINTERING CHARGE The present invention relates to improvements in a method and apparatus for establishing the firing temperature curve of a charge fired on the travelling grate of a sintering'machine.

As is known, agglomerates are produced by loading a mixture of a combustible solid material and a particulate ore of a predetermined mesh size on the grate of an endless moving chain, and subjecting the mixture to firing by a flame while causing the front of the flame to penetrate into the mixture by drawing air through the mixture from below the grate. Throughout the specification and claims, the term frontof the flame designates the plane of separation between the part of the mixture which has been combusted and the remainder of the mixture. The formation of the agglomerated product results from the mineralogical transformation of the charge as a result of the fusion in the combustion zone.

The quality of the agglomerate depends largely on the firing temperature of the product. Since the sintering has as its object a product of well defined and regular properties, it is useful to obtain criteria of the front of the flame which may be utilized as control parameters for the movement of the sintering chain. In this connection, it has been recognized that the temperature of the gases which have passed through the charge may be used as such a control. Experimental work with a static experimental model has shown a characteristic development of the temperature of these gases which is tied to the front of the flame, the temperature curve beginning characteristically with a plateau of a more or less constant temperature, followed by a steeply rising curve portion corresponding to the arrival of the front of the flame at the grate, and then a temperature decline. The shape of this curve gives useful information about the progress of the sintering process.

Since the same phenomena occur on a sintering chain, a curve of the same shape must be found, the time scale in the static experimental model being re placed by the ordinate of the length of the moving chain since each portion of the charge is constantly displaced during the sintering. Methods to trace such temperature curves have been proposed wherein the temperature of the gases passing through the sintered charge is continuously measured by means of a series of temperature sensitive devices arranged below the chain.

These methods have not been entirely satisfactory, however, because the charge in an industrial operation is not regular, which produces deformations in the curve which are not reflective of like variations in the firing temperature. Temerefore, Therefore, curve recorded under such conditions cannot serve as a reliable reference revealing deviations in respect of the optimum speed of the chain movement. To trace a curve which truly reflects deviations in the movement of the chain, means must be found to isolate a portion of the charge on the chain and to follow this portion throughout its passage through the sintering zone while noting the development of the temperature of the gases which pass through this portion of the charge.

Merely arranging a temperature sensitive device below a carriage of the chain wherein the portion of the charge is loaded is not sufficient for satisfactory industrial results because this does not give information at each pass of the chain. While it is possible to reduce the period of the temperature reading by increasing the number of temperature sensitive devices, this becomes onerous.

It is the primary object of this invention to provide an improved method and apparatus of establishing in a continuous manner the firing temperature curve of a charge loaded on a moving endless chain by means of a static measuring assembly.

In this method, successive portions of the charge are loaded on the grate of a moving; chain or conveyor, each portion of the charge is fired and gases are drawn through the tired portion of the charge from below the grate. ln accordance with the invel ition, the temperature of the gases which have passed through the fired portion of the charge is measured at points spaced longitudinally in the direction of the movement of the chain below the grate, and the speed of the movement of the chain is also measured. To obtain the desired re sult, i.e., a firing temperature curve of the same portion of the charge, the temperature measurement and the speed measurement are so coordinated that the ternperature measurement depends on the speed measurement. The temperature measurements are sampled periodically in such a manner that a series of temperature values taken at a succession of the spaced points corresponds to the temperature of the gases which successively traversed each portion of the charge during the movement of the chain. The coordination of the measurements consists in making instantaneous readings of the temperature values each time the chain moves a distance equal to the spacing of the temperature measuring points. Thus, the temperature readings take place only when the portion of the charge which has passed one measuring point reaches the next following measuring point. The entire series of temperature values is transmitted to a 'memory where it is stored and may then be extracted or retrieved when the portion of the charge has passed above the last temperature measuring point to obtain the firing temperature curve for this portion of the charge. This curve cannot actually be completed until all temperature values have been obtained for this curve.

In the improved apparatus of the present invention, a row of successive, linearly arranged temperature sensitive devices is arranged below the grate of a moving chain or conveyor whereon successive portions of the charge are loaded, which devices are spaced longitudinally in the direction of movement of the chain. In order to obtain coherence of the temperature measurement, the devices have temperature sensitive ends lying substantially in a common horizontal plane closely adjacent and substantially parallel to the grate. Means is provided for measuring the speed of the movement of the chain, and means is connected to the temperature sensitive devices for receiving signals corresponding to the sensed temperatures. Means responsive to the speed measuring means performs instantaneous temperature readings of the values measured by the temperature sensitive devices each time the chain has moved a distance corresponding to the spacing be-- tween the devices. The information corresponding to the received signals is transmitted to a memory. and means is provided to retrieve the transmitted information to obtain the firing temperature curve each time one of the charge portions has passed above all the temperature sensitive devices.

According to a preferred embodiment, the temperature sensitive devices are substantially equidistantly spaced from each other. This permits the synchronization of the temperature and chain movement speed measurements to be simplified.

The temperature sensitive devices are preferably thermocouples held in tubes of non-oxidizable steel.

The means for measuring the speed of the chain movement may advantageously comprise photoelectric cells actuated by spaced markers on the chain to emit control signals when respective markers pass the cells.

Finally, the synchronizing means may include an electronic assembly receiving control signals emitted by detector means mounted along the path of the moving chain, with the signal receiving assembly emitting a pulse each time the chain has moved the distance of the spacing between the thermocouples.

As will become more apparent from the following detailed description, the row of temperature sensitive devices is linearly disposed in the direction of the chain movement, each device being static. Thus, n points of the firing temperature curve are obtained by N temperature sensitive devices arranged in a row. By interconnecting the points, one obtains the curve of the temperature of the gases which have passed through the sintering zone.

The curve is built as follows:

N temperature sensitive devices C C C are aligned in a row in the direction of displacement of the chain. In the time t a portion E of the charge passes above temperature sensitivedevice C which delivers a corresponding temperature value 0,. At the end of time t,, the portion E has moved to pass above device C which produces value 0 for-the same portion, and so on. If the distance between adjacent temperature sensitive devices is equal, say L, and if V is the speed of the chain movement, the following relationship holds:

and at the end of a time T equal to the sum of the times 2,, N values 0 0 0 will represent N points on the curve. In practice, a temperature value sensed by the N temperature sensitive devices is transmitted at each instant T, 2T and these values are transmitted to a memory. These values-are then retrieved as and when the information relating-to a curve has been completed, i.e., each time a portion of the charge passes over the Nth temperature sensitive device. Thus, the firing temperature curve for the portion E of the charge is not obtained until after it has passed over the Nth device.

If several parallel rows of temperature sensitive devices are arranged below the chain, several curves are obtained for the same portion of the charge, indicating the quality of the fired charge in a transverse direction, which is most useful in controlling the loading of the chain.

The above and other objects, advantages and features of the present invention will become more apparent from the following detailed description of now preferred embodiments thereof, taken in conjunction with the accompanying drawing wherein FIG. 1 is a schematic cross sectional view of a travelling grate sintering machine equipped with temperature measuring devices and chain movement speed detectors according to this invention;

FIG. 2 is a schematic top view of one particular arrangement of temperature measuring devices; and

FIG. 3 shows a recorded temperature curve of the gases.

Referring now to the drawing and first to FIG. 1, the generally conventional endless sintering chain 1 is shown schematicaly and only partially, the chain being constituted by a series of carriages running on wheels and holding the charges 2. The charges are fired by a flame producing device 3, which may be a row of burners, the endless chain 1 moving the charges under and past the burner means 3. Subsequent to the burner means, in the direction of the movement of the chain, two wind boxes 4 and 5 are mounted below the chain to draw air from below through the charges 2, the bottoms of the carriages being grates which hold the charges and permit air to be drawn therethrough. In this manner, the front or tip of the flame is caused to pass into the charges vertically downwardly.

Temperature sensitive devices 6a 6n are mounted in the walls of the wind boxes and extend with the temperature sensitive tips 7 into the wind boxes, the temperature sensitive tips 7 extending to a common plane P parallel to the chain and close to the carriages holding the fired charges. The temperature sensitive tips 7 are equidistant from each other, being spaced by a distance L in the plane P.

Chain movement speed detectors 8a, 8b, 8c are arranged along the path of the chain to determine the speed of the chain movement. In the illustrated embodiment, these detectors are photoelectric cells which detect the passage of reference marks on the carriages of the chain. These reference marks may simply be the wheels of the carriages whose distance from each other is known. Upon passage of a reference mark in front of a photocell, a control signal is emitted by the cell. The cells 8a, 8b, 8c are connected to an electronic assembly 9 which receives the signals to determine the speed of the chain movement. The assembly 9 is arranged to emit a signal each time the chain has advanced a distance L corresponding to the distance between the temperature sensitive probes 6a 6n. Since an electronic device producing signals on the basis of information of the detected passage of marks is conventional, it is not further described and illustrated to avoid prolixity.

Another conventional electronic assembly 10, for instance a computer, is connected to all of the temperature sensitive devices which emit control signals corresponding to the sensed temperatures. These signals are transmitted to computer 10 which is also connected to electronic assembly 9. When the computer 10 receives a signal from assembly 9, which indicates that the chain 1 has moved distance L, it triggers the reading of the temperature of all temperatures sensitive devices 6a 6n, simultaneously recording the readings in memory 11. Thus, it will be seen that, each time the chain advances a distance L, a series of temperature readings of n elements of charge 2 are recorded. When the charge 2 has passed above all of the temperature sensitive devices, the temperature values relative to this charge can be obtained from the memory 1 1, and it is thus possible to trace the firing curve of the charge.

Thus, a static device is used to obtain a curve representing the temperature of the gases which have traversed the charge during its passage by synchronizing the measurements of the temperature and of the chain movement. Thus, a continuous control is obtained on the basis of firing temperature curves each representative of one charge, the charges being separated from each other by the same distance, as the distance between the temperature sensitive devices.

In the schematic view of FIG. 2, three parallel rows of temperature sensitive devices 6a, 6a, 6a" are arranged along the chain. Such an arrangement gives a refined reading of the charge tempratures and, more particularly, gives information about the regularity of the charge in a transverse direction. In this modification, the arrangement is generally the same as that of FIG. ll, except that the memory must be arranged to receive and record three sets of information simultaneously, as received from three transversely aligned temperature sensitive devices. in a practical embodiment, the central row of temperature sensitive devices 6a may be placed along the center line of the chain while the two rows of devices 6a and 6a" are placed on either side of the central row at a same given distance from the edge of the chain.

The following example shows the practice of the invention on an otherwise conventional sintering chain which produces 250 tons of agglomerates per hour, with a total grate surface of 196 sq. m., a length of 56 m, and a width of 3.5 m. The distance L between the thermo-sensitive devices was fixed at 0.5 m. and the thermosensitive tips thereof were placed 0.5 m. below the grate. This distance of the thermosensitive devices produces a measuring frequency between 5 and 10 seconds when the chain movement speed varies between 6 and 3 m./min. The chosen thermo-sensitive devices were chromel/alumel thermocouples of 1.5 mm. diameter, mounted in the interior of non-oxidizable steel tubes.

FIG. 3 shows a firing temperature curve obtained with this apparatus. The curve follows the experimentally established outlines, i.e., a stable temperature zone AB, a steeply rising temperature zone BC and finally a cooling-off zone CD. The point C on the curve indicates the penetration of the front of the flame and gives the final firing temperature of the charge.

As indicated in H6. l, the thermocouples are equally distributed in the wind boxes but certain industrial installations willrnake such an ideal arrangement impossible. in this case, some of the thermocouples may be omitted, which simply means an absence of some points on the curve. However, this will affect only a few points on the curve and will leave the same, for practical purposes, sufficiently definite.

Also, while the equidistant arrangement of the thermocouples exemplified herein is the simplest arrangement from the point of view of the synchronization of the measurements, it is also feasible to space the thermocouples at random distances. This will require a more complex synchronization mechanism to take into account the different spacings and to disconnect the reading or taking of the temperatures as a function of the proper position of each thermocouple and the speed of the movement of the chain.

Whatever the chosen arrangement, the present invention permits the tracing of a series of curves each representing the temperature of the gases traversing a given portion or element of the charge. Since each curve is representative of a distinct charge portion, parasitic effects resulting particularly from different conditions in different charge portions are avoided. This is a considerable advantage over known methods because it becomes possible to isolate and. to detect variations resulting solely from the front of the flame which is the important factor in the quality of the product.

We claim:

1. An apparatus for establishing the firing temperature curve of successive portions of a charge to be sintered, comprising 1 a moving chain including a grate for loading successive portions of said charge and carrying markers at a known spaced relationship in the direction of movement, I

2 burner means for firing each portion of the charge and means for drawing gases through the fired portion of the charge arranged below the grate,

3 a row of successive linearly arranged temperature sensitive devices arranged below the grate and spaced longitudinally in the direction of movement of the chain,

a said devices having temperature sensitive ends lying substantially in a common horizontal plane closely adjacent the grate,

4 speed measuring means for measuring the speed of the movement of the chain, said measuring means including photoelectric cellls actuated by said markers to emit control signals when respective ones of said markers pass the cells,

5 means connected to the temperature sensitive devices and receiving signals corresponding to the sensed temperatures,

6 means responsive to said control signals for triggering the signal receiving means for temperature recording each time the chain has moved a distance corresponding to the spacing between the temperature sensitive devices, and

7 means for transmitting the information corresponding to the received signals to a memory and to retrieve the transmitted information to obtain the firing temperature curve each time one of said charge portions has passed above all the temperature sensitive devices.

2. An apparatus for establishing the firing temperature curve of successive portions of a charge to be sintered comprising 1 a moving chain including a grate for loading successive portions of said charge and carrying markers at a known spaced relationship in the direction of movement, i

2 burner means for firing each portion of the charge and means for drawing gases through the fired portion of the charge arranged below the grate,

3 a row of successive linearly arranged temperature sensitive devices arranged below the grate and spaced longitudinally in the direction of movement of the chain,

a said devices having temperature sensitive ends sying substantially in a common horizontal plane closely adjacent the grate,

4 speed measuring means for measuring the speed of the movement of the chain, said measuring means including stationary detecting means arranged adjacent said chain for detecting said markers as the markers pass said detecting means, and responsive to the passing of respective detected markers for emitting control signals,

ing temperature curve each time one of said charge portions has passed above all the temperature sensitive devices.

3. The apparatus of claim 2, wherein the temperature sensitive devices are substantially equidistantly spaced from each other.

4. The apparatus of claim 2, wherein the temperature sensitive devices are thermocouples mounted in tubes of non-oxidizable steel. 

1. An apparatus for establishing the firing temperature curve of successive portions of a charge to be sintered, comprising 1 a moving chain including a grate for loading successive portions of said charge and carrying markers at a known spaced relationship in the direction of movement, 2 burner means for firing each portion of the charge and means for drawing gases through the fired portion of the charge arranged below the grate, 3 a row of successive linearly arranged temperature sensitive devices arranged below the grate and spaced longitudinally in the direction of movement of the chain, a said devices having temperature sensitive ends lying substantially in a common horizontal plane closely adjacent the grate, 4 speed measuring means for measuring the speed of the movement of the chain, said measuring means including photoelectric cells actuated by said markers to emit control signals when respective ones of said mArkers pass the cells, 5 means connected to the temperature sensitive devices and receiving signals corresponding to the sensed temperatures, 6 means responsive to said control signals for triggering the signal receiving means for temperature recording each time the chain has moved a distance corresponding to the spacing between the temperature sensitive devices, and 7 means for transmitting the information corresponding to the received signals to a memory and to retrieve the transmitted information to obtain the firing temperature curve each time one of said charge portions has passed above all the temperature sensitive devices.
 2. An apparatus for establishing the firing temperature curve of successive portions of a charge to be sintered comprising 1 a moving chain including a grate for loading successive portions of said charge and carrying markers at a known spaced relationship in the direction of movement, 2 burner means for firing each portion of the charge and means for drawing gases through the fired portion of the charge arranged below the grate, 3 a row of successive linearly arranged temperature sensitive devices arranged below the grate and spaced longitudinally in the direction of movement of the chain, a said devices having temperature sensitive ends sying substantially in a common horizontal plane closely adjacent the grate, 4 speed measuring means for measuring the speed of the movement of the chain, said measuring means including stationary detecting means arranged adjacent said chain for detecting said markers as the markers pass said detecting means, and responsive to the passing of respective detected markers for emitting control signals, 5 means connected to the temperature sensitive devices and receiving singals corresponding to the sensed temperatures, 6 means responsive to said control signals for triggering the signal receiving means for temperature recording each time the chain has moved a distance corresponding to the spacing between the temperature sensitive devices, and 7 means for transmitting the information corresponding to the received signals to a memory and to retrieve the transmitted information to obtain the firing temperature curve each time one of said charge portions has passed above all the temperature sensitive devices.
 3. The apparatus of claim 2, wherein the temperature sensitive devices are substantially equidistantly spaced from each other.
 4. The apparatus of claim 2, wherein the temperature sensitive devices are thermocouples mounted in tubes of non-oxidizable steel. 